Pad-lifting

[Cursitor Doom]

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

thanks

 

[John-Del]

On Tuesday, February 9, 2016 at 6:26:21 AM UTC-5, Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

thanks

Preheat the board before desoldering and apply some liquid flux. Make sure to use *enough* heat as too low is just as bad as too much. You want to reduce the time it takes to finish the process more than anything.

 

[Cydrome Leader]

Cursitor Doom <curd@notformail.com> wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

Add fresh solder and liquid flux, then solder suck or use braid.

old solder has oxides and crap on it and is a poor heat conductor, so you
you can end up burning the pads off the board if you fight with it too
long. Cutting Leads off the part can help too if they were wedged into the
holes.

 

[Adrian Caspersz]

On 09/02/16 11:23, Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

Tip on a more powerful iron?

--
Adrian C

 

[Chuck]

On Tue, 9 Feb 2016 12:14:32 +0000, Adrian Caspersz
<email@here.invalid> wrote:

On 09/02/16 11:23, Cursitor Doom wrote:
Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

Tip on a more powerful iron?

Been using this one professionally for years.
http://www.mcmelectronics.com/product/TENMA-21-147-/21-147

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Geo]

On Tue, 9 Feb 2016 11:23:24 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

I used to service scopes and DVMs and other testgear in the service
department of the manufacturer. At the time they did not use surface
mount so any duff IC, transistor, diode etc had all its pins cut on
the top of the board then each pin removed individually (using spring
loaded solder sucker or vacuum device depending if in field or not).

 

[N_Cook]

On 09/02/2016 11:23, Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

thanks

At least you don't need fume extraction as no throat-grabbing noxious
PbF stuff.
Go around each blob with fresh multicore solder, heating just enough to
introduce some new solder, but no great depth.
Then long nose pliers on the other side of the board and as much tug as
you can give, while reheating the solder. Repeat for each pad.

 

[N_Cook]

On 09/02/2016 15:24, N_Cook wrote:

On 09/02/2016 11:23, Cursitor Doom wrote:
Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

thanks


At least you don't need fume extraction as no throat-grabbing noxious
PbF stuff.
Go around each blob with fresh multicore solder, heating just enough to
introduce some new solder, but no great depth.
Then long nose pliers on the other side of the board and as much tug as
you can give, while reheating the solder. Repeat for each pad.

Then when finished, a needlepoint (steel ,not S/S needle set in a pencil
or something as a handle) set point in the hole , heating the needle
with soldering iron while pushing through pcb and waggling , to give
good clean h

 

[Jeff Liebermann]

On Tue, 9 Feb 2016 11:23:24 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.
thanks

My advice tends to go against conventional wisdom and some of the
other advice in this thread. The problem is that you're delivering
too many joules for too long a time (Joules = watt-seconds). To avoid
problems, you have to work fast. You can get the joint as hot as you
want, but not for very long.

Therefore, I suggest:
1. Don't use this type of soldering iron:
<http://stellartechnical.com/images/213.jpg>
2. Use an 850F solder tip, not 750F. Work fast.
3. Use a medium size tip. Too big and it will deliver too many
joules. Too small and de-soldering will take too long.
4. Don't mix lead free and Pb-Sn solder.
5. Don't use solder wick. A solder sucker works faster.
6. Hit the connection with some solder before unsoldering to make the
old solder flow. Slopping flux on the pad doesn't help because the
flux will vaporize before the solder melts.
7. If the PCB is phenolic, the pads always lift.

I'm undecided if hot air desoldering is any better than a soldering
sucker for through hole parts.

Conformal coatings such as urethane or acrylic, will either burn or
vaporize before the solder melts. Using these to glue down the pad
doesn't seem to work for me.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Ian Field]

"John-Del" <ohger1s@aol.com> wrote in message
news:d227f504-89c1-4d6e-bed2-79397429db9b@googlegroups.com...

On Tuesday, February 9, 2016 at 6:26:21 AM UTC-5, Cursitor Doom wrote:
Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

thanks

Preheat the board before desoldering and apply some liquid flux. Make
sure to use *enough* heat as too low is just as bad as too much. You want
to reduce the time it takes to finish the process more than anything.

I'd add to that; make sure the end of the lead isn't bent so it struggles
when you try to pull it out.

Although its my preferred method, I'm reluctant to recommend a piston type
solder sucker because the recoil can knock pads off if you're not careful.
Conversely; solder wick has to be kept hot while you pull it away, or the
pad/track comes with it - which doesn't really help with keeping the heating
to the shortest time possible.

Sometimes you have to remove the solder to inspect the end of the lead, and
straighten it if required. All I can suggest is; use the method you're most
comfortable with.

A single sided board is dead easy if you remove the solder, through hole
takes a little more effort. Some manufacturers do sucker irons where the tip
is hollow and has a receptacle for the waste solder, the expensive ones with
an electric pump or the cheaper type with a rubber bulb next to the handle.
It almost never removes *ALL* the solder from a through hole, but you can
usually wiggle the lead free with pointy nose pliers.

In most cases more solder and the flux that comes with it is added to
improve heat flow - in the case of RoHS solder, adding some 60/40 lowers the
melting temperature.

 

[John Robertson]

On 02/09/2016 4:14 AM, John-Del wrote:

On Tuesday, February 9, 2016 at 6:26:21 AM UTC-5, Cursitor Doom wrote:
Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

thanks

Preheat the board before desoldering and apply some liquid flux. Make sure to use *enough* heat as too low is just as bad as too much. You want to reduce the time it takes to finish the process more than anything.

I constantly am working on boards that are from the 1970s. Mostly I use
a #7 tip on my Weller solder station, and a Soldapullt (sp?) solder
sucker. Take great care not to push down on the solder pad, press the
tip sideways. Do NOT let the solder sucker strike the tip when sucking
the solder, but keep it on a 45 degree angle away from the tip, with its
tip resting on the PCB.

Have the PCB well supported if possible so it doesn't bounce.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Jon Elson]

Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

OY! It depends a lot on the quality of the board, and then how much heat it
has been exposed to, over its life.

If the chip is no good, I scribe the leads with an X-acto knife, running
down the whole row, and then JUST BARELY snap the leads off from the body.
You only have to do this on one side of a SOIC. Then scribe the other side
and bend the IC up and down a few times, until it breaks off completely.
Then, the individual leads can be removed in a much more gentle fashion.
Avoid pressing down on the pads, they will tend to "crumple" and the edges
pull up from the board.

Since you say OVER 25 years, I'm guessing none of this is SMT? If it has
plated through holes, these generally are quite robust. The worst are some
old paper-phenolic one-sided boards. You just look at them and the pads
start coming off.

There are mass desoldering tools for DIP and SOIC standard sizes that work
pretty well to melt the solder on all leads simultaneously. These work
great if you have the right size. I've even made some custom ones out of
solid copper bar when I had a bunch of chips to pull.

And, of course, a temperatur-controlled soldering iron, run at the minimum
temperature possible, is a big help.

Jon

 

[Jon Elson]

John Robertson wrote:

Soldapullt (sp?) solder
sucker.

These work, but if you have ever used a Pace desoldering station with either
a vacuum pump or a venturi suction generator, you will be AMAZED at how much
better a job it does. These have a hollow copper tip, so you can keep the
tip on the joing while it applies the suction. You apply the tip, wait a
few seconds and then wiggle the tip in an orbiting motion and step on the
pedal. When the slurping sound stops, all the solder is gone, let up on the
pedal and remove the tip. There is no big reaction from a flying piston as
with the plugner-type solder puller, and you get enough suction time to get
ALL the solder out of the joint.

(Other brands of pump-type desoldering irons are probably just as good, but
I happen to have Pace brand gear.)

Jon

 

[Gareth Magennis]

"Jon Elson" wrote in message
news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com...

Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.

OY! It depends a lot on the quality of the board, and then how much heat it
has been exposed to, over its life.

If the chip is no good, I scribe the leads with an X-acto knife, running
down the whole row, and then JUST BARELY snap the leads off from the body.
You only have to do this on one side of a SOIC. Then scribe the other side
and bend the IC up and down a few times, until it breaks off completely.
Then, the individual leads can be removed in a much more gentle fashion.
Avoid pressing down on the pads, they will tend to "crumple" and the edges
pull up from the board.








I still use a similar method when it suits.
Get a new blade in your knife, and you can quite easily cut vertically
through all the pins on any sized DIL (or SMD) device with no damage to the
PCB, with a bit of practice of course.

(Some SMD devices are glued quite hard to the PCB, making desoldering a
nightmare, but once they have no legs you can safely chisel the body off
the board and wipe away the legs individually)


Gareth.

 

[Ian Field]

"Jon Elson" <jmelson@wustl.edu> wrote in message
news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com...

Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.
OY! It depends a lot on the quality of the board, and then how much heat
it
has been exposed to, over its life.

If the chip is no good, I scribe the leads with an X-acto knife, running
down the whole row, and then JUST BARELY snap the leads off from the body.

A Swan & Mortem scalpel is a little more precise for the smaller ICs,
Usually I shear the pins off at the header - but you have to be careful not
to slice tracks underneath.

With the old standard pitch DIL packages, a decent quality pair of side
cutters were sufficient to nip the pins off flush with the header.

 

[Ian Field]

"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:Xjsuy.834766$QP2.201595@fx42.am4...

"Jon Elson" wrote in message
news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com...

Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.
OY! It depends a lot on the quality of the board, and then how much heat
it
has been exposed to, over its life.

If the chip is no good, I scribe the leads with an X-acto knife, running
down the whole row, and then JUST BARELY snap the leads off from the body.
You only have to do this on one side of a SOIC. Then scribe the other
side
and bend the IC up and down a few times, until it breaks off completely.
Then, the individual leads can be removed in a much more gentle fashion.
Avoid pressing down on the pads, they will tend to "crumple" and the edges
pull up from the board.








I still use a similar method when it suits.
Get a new blade in your knife, and you can quite easily cut vertically
through all the pins on any sized DIL (or SMD) device with no damage to
the PCB, with a bit of practice of course.

There's a bit of a knack to it, you carve through the pins at a slight angle
and make sure the blade edge lands squarely on the PCB underneath without
any sliding/slicing motion.

If you avoided using too much force, any tracks underneath usually survive
unscathed.

One trick I've heard about, is to feed some thin wire under an SMD chip and
ease it out sideways while applying heat, lifting the pins as it goes - but
this doesn't exactly fit in with the advice to minimise the duration of
applied heat. It probably wouldn't help at all if the pads are fragile to
start with.

 

[John Robertson]

On 02/09/2016 12:44 PM, Jon Elson wrote:

John Robertson wrote:

Soldapullt (sp?) solder
sucker.

These work, but if you have ever used a Pace desoldering station with either
a vacuum pump or a venturi suction generator, you will be AMAZED at how much
better a job it does. These have a hollow copper tip, so you can keep the
tip on the joing while it applies the suction. You apply the tip, wait a
few seconds and then wiggle the tip in an orbiting motion and step on the
pedal. When the slurping sound stops, all the solder is gone, let up on the
pedal and remove the tip. There is no big reaction from a flying piston as
with the plugner-type solder puller, and you get enough suction time to get
ALL the solder out of the joint.

(Other brands of pump-type desoldering irons are probably just as good, but
I happen to have Pace brand gear.)

Jon

I HAVE a Pace Desoldering station (actually two of them) - however I am
usually just removing one or two ICs and I can remove them with my
Weller (#7!) and Soldapullt faster than the Pace will heat up!

You can get a nice rhythm going where you heat two leads at the same
time (medium tip) and suck both together, then while the next pair are
warming up you are reloadng the sucker with your other hand. I can pull
a 40 pin chip in a minute or less typically (not that I ever time
myself, it just seems to go pretty fast.).

Once the legs are unsoldered I then use a tiny screwdriver to push the
bottom leads back and forth across the feed through hole. If it appears
to be stuck I put a dab of solder and resuck. Then I press the bottom of
each leg on the top side where they meet the PCB to again loosen them
up. At this point the IC usually pulls out with my finger tips. Prying
with any force at all means something is wrong...not to mention it yanks
out feed through pipes!

If I am reworking a bunch of chips then the Pace is heated up. It is
slightly better as you can put the tip around the IC's lead and swirl it
from side to side as you heat it up, to feel if it has released, prior
to suction.

John :-#)#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."

 

[Jon Elson]

John Robertson wrote:

I HAVE a Pace Desoldering station (actually two of them) - however I am
usually just removing one or two ICs and I can remove them with my
Weller (#7!) and Soldapullt faster than the Pace will heat up!

Yes, this is absolutely true! But, for something really expensive, or where
I have a lot of pins to desolder, I take the time to warm up the Pace, and
always get GREAT results. Usually the part just falls off the board when
the last pin is desoldered.

You can get a nice rhythm going where you heat two leads at the same
time (medium tip) and suck both together, then while the next pair are
warming up you are reloadng the sucker with your other hand. I can pull
a 40 pin chip in a minute or less typically (not that I ever time
myself, it just seems to go pretty fast.).

Once the legs are unsoldered I then use a tiny screwdriver to push the
bottom leads back and forth across the feed through hole. If it appears
to be stuck I put a dab of solder and resuck.

With the Pace, and the technique of orbiting the tip while applying suction,
I RARELY have this happen. Usually, I desolder the whole chip and it just
falls off the board. That wigglign back and forth can damage the plated
barrel of the hole.

Jon

 

[Gareth Magennis]

"Ian Field" wrote in message news:QAsuy.601143$pB6.586499@fx41.am4...



"Gareth Magennis" <sound.service@btconnect.com> wrote in message
news:Xjsuy.834766$QP2.201595@fx42.am4...

"Jon Elson" wrote in message
news:eLGdneB9Lc6Y0yfLnZ2dnUU7-bednZ2d@giganews.com...

Cursitor Doom wrote:

Hi all,

Anyone got any tips on how to avoid the unpleasant situation where you
try to de-solder a part on an elderly board and end up removing more than
just component leads? Most of the stuff I work on is at *least* 25 years
old and things start to get fragile.
OY! It depends a lot on the quality of the board, and then how much heat
it
has been exposed to, over its life.

If the chip is no good, I scribe the leads with an X-acto knife, running
down the whole row, and then JUST BARELY snap the leads off from the body.
You only have to do this on one side of a SOIC. Then scribe the other
side
and bend the IC up and down a few times, until it breaks off completely.
Then, the individual leads can be removed in a much more gentle fashion.
Avoid pressing down on the pads, they will tend to "crumple" and the edges
pull up from the board.








I still use a similar method when it suits.
Get a new blade in your knife, and you can quite easily cut vertically
through all the pins on any sized DIL (or SMD) device with no damage to
the PCB, with a bit of practice of course.

There's a bit of a knack to it, you carve through the pins at a slight angle
and make sure the blade edge lands squarely on the PCB underneath without
any sliding/slicing motion.

If you avoided using too much force, any tracks underneath usually survive
unscathed.




Yep, that's my method exactly. More of a Guillotine action.


Gareth.

 

[Bob Engelhardt]

Has anyone ever used pressure to blow away solder? I'm thinking that
125 psi through a tiny nozzle would clean out the solder better than a
spring loaded solder sucker.

Though I guess that it might send molten solder where you don't want it!

Bob